1. Field of the Invention
The present invention relates to an electronic device such as a transmitter/receiver unit housed in a portable telephone, in which heat discharge and weight reduction are considered.
2. Related Art
A portable telephone is required to be light, compact, and further, shock-resistant.
As shown in FIGS. 4 and 5, a conventional electronic device, for example, a transmitter/receiver unit for a portable telephone comprises a box-shaped frame member 52, an upper cover 53 covering the top face of the frame member 52, a lower cover 54 covering the under face of the frame member 52, and a printed board 51 housed in the frame member 52.
The transmitter/receiver unit is soldered to the main printed board of the body (not shown) by using metal terminals 56 which will be described later and constructs a portable telephone.
The frame member 52 has four side walls 52a formed by bending a solder-plated or tinned metal plate, openings 52b which are formed to be open upward and downward in the side walls 52a, and the metal terminals 56 used for both attachment and grounding extended integrally from the side walls 52 at the four corners of the side walls 52a.
A copper foil pattern (not shown) having high thermal conductivity is formed on the face of the rectangular-shaped printed board 51. The copper foil pattern is constructed by a land on which electronic parts 50 such as a power amplifier IC for transmission, a resistive element, a capacitor, and the like are soldered and a circuit pattern in which the electronic parts 50 are electrically connected. Further, a circuit pattern is formed for grounding around the printed board 51. The printed board 51 is housed so as to be fit almost in an intermediate position in the vertical direction of the inner faces of the side walls 52a of the frame member 52 and is electrically connected to the frame member 52.
The upper cover 53 is a solder-plated or tinned metal plate. The upper cover 53 has a notched and lowered part 55 formed by notching a part of a flat part 53a and bending it inside and a plurality of bent parts 53b formed by bending the periphery of the flat part 53a. The upper cover 53 is attached so as to cover the upper opening 52b of the frame member 52 and so that the inner sides of the bent parts 53b are fit on the outer faces of the side walls 52a.
The notched and lowered part 55 is arranged in a position to face from the above the electronic part 50, especially, the power amplifier IC for transmission on the printed board 51 assembled in the frame member 52. In this instance, the electronic part 50 is in contact with the notched and lowered part 55.
The lower cover 54 is made of the same material and has the same size as the upper cover 53. In the lower cover 54, a plurality of bent parts 54b are formed by bending the periphery of a flat part 54a in one direction. In a manner similar to the upper cover 53, the lower cover 54 is attached so as to cover the lower opening 52b of the frame member 52 and so that the inner sides of the bent parts 54c are fit on the outer faces of the side walls 52a.
Such a transmitter/receiver unit for a portable telephone discharges heat generated from the electronic parts 50, especially, from the power amplifier IC for transmission and the like to the outside by thermal conduction via the notched and lowered part 55 and the upper cover 53 connected to the notched and lowered part 55.
A conventional electronic device, especially, the transmitter/receiver unit for a portable telephone is constructed so as to discharge the heat generated by the electronic part from the cover via the notched and lowered part. Since the transmitter/receiver unit has a structure that it is covered with the metal frame member and upper and lower covers, although it has a heat discharging effect, there is a problem such that the unit is relatively heavy and it is difficult to reduce the weight.